1. Field of the Invention
The present invention relates to a coextruded multilayer laminate which is useful as an outdoor construction material, and more particularly relates to coextruded multilayer laminates which have a protective vinyl chloride polymer superstrate layer and a protected vinyl chloride polymer substrate layer.
2. Description of the Related Art
The use of vinyl chloride polymers as resin compositions for forming construction materials for external use, for example, residential siding, is known, see Canadian Patent No. 996,329 and McDonagh, U.S. Pat. No. 4,169,180, issued Sep. 25, 1979, which is incorporated herein by reference. Such materials have typically required impact modification, and typically butylacrylate rubber based graft copolymers, such as 2-propenoic acid 2-methyl methylester polymer with less than 10% 1,3 butadiene and butyl 2-propenoate polymer or methyl methacrylate butylacrylate polymer graft polymers, have been used to impact modify these vinyl chloride polymer compositions due to the inherent weatherability of butylacrylate rubbers. Butadiene type graft copolymers, such as acrylonitrile-butadiene-styrene graft copolymers have not typically been utilized to impact modify such vinyl chloride polymeric compositions, due to the historically perceived weatherability problems of such materials for external siding applications. Note the teachings of the McDonagh patent, U.S. Pat. No. 4,169,180, issued Sep. 25, 1979, which on column 1, line 65 to column 2, line 5, sets out that resins such as acrylonitrile-butadiene-styrene, methylmethacrylate-butadiene-styrene, and high impact polystyrene have the necessary strength to be used as outdoor construction materials, but which nevertheless undergo deterioration in their mechanical properties or discoloration when used outdoors and subjected to ultraviolet light and environmental degradation.
The use of butylacrylate acrylate rubber graft polymers as impact modifiers for vinyl chloride polymeric compositions requiring resistance to the weathering elements of heat, ultraviolet light, and moisture, have, however, had several problems, including relatively low impact strength compared to similar rubber loadings of butadiene based graft polymers, and have typically caused the vinyl chloride polymer compositions to fuse too slowly resulting in the vinyl chloride polymers not obtaining their desired level of natural ductility due to failure to knit well, thereby requiring processing aids and higher processing temperatures and limiting output rates. Impact strength of the vinyl chloride compositions containing the butylacrylate graft polymer can be enhanced by utilizing more butylacrylate (for example, to improve the low temperature impact of the composition), and more processing aids can be employed in the compositions, but both of these add undesired increased material costs to the final product.
Accordingly, there is a need to provide vinyl chloride polymer compositions for outdoor construction materials which exhibit improved low temperature impact strengths at a given rubber loading level, which exhibit increased fusion speeds for the vinyl chloride polymer without the utilization of excessive processing aids, and which utilizes butadiene based graft copolymers avoiding perceived weatherability issues associated with such materials in outdoor construction applications.